Laboratory examination of greenhouse gaseous and microbial dynamics during thawing of frozen soil core collected from a black spruce forest in Interior Alaska

ABSTRACTIn this study, we conducted an incubation experiment on a frozen soil core collected from a black spruce forest in Interior Alaska, in order to investigate potential changes in greenhouse gaseous (GHG) and microbial dynamics during thawing of frozen soil. The soil thawing is an important environmental process determining the annual GHG balance in the northern high-latitude ecosystem. A core spanning the ground surface to upper permafrost with a depth of 90 cm was vertically grouped into three layers (top, middle, and bottom layers). Then, 12 soil samples from 3 layers (i.e., 4 soil samples per layer) were incubated for 3 weeks, and net carbon dioxide (CO2) and methane (CH4) release/uptake rates were estimated. During the incubation, temperature was changed weekly from 0 to 5, then 10°C. The net amounts of CO2 released by six of the eight soil samples from the top and middle layers were 1.5–19.2-fold greater at 5°C than at 0°C, while the release at 10°C was reduced in the cases of three of these si...